On Wednesday, Physicians for Human Rights (PHR), a New York-based medical watchdog group, released a new interactive map and report showing that Syrian forces have been committing systematic attacks on medical personnel and facilities in opposition-held areas, resulting in the death of more than 460 medical staff.

The organization said government forces committed 90 percent of a confirmed 150 attacks on 124 facilities between March 2011 and March 2014 and that its map, which will be updated regularly, is “the most comprehensive resource on attacks on medical care in Syria.”

Before the conflict, Syria had one of the best-developed health care systems in the Arab world. Today, the U.N. estimates that 245,000 Syrians are living in besieged areas, cut off from medical supplies, and that almost half of the country’s public hospitals have been partially or totally destroyed.

We asked Erin Gallagher, PHR’s director of emergency investigations and response, to weigh in on who is targeting facility and personnel, how the attacks vary in urban and rural areas, and the toll they have taken on Syria’s medical staff.

Syria Deeply: What exactly is being targeted, and how?

Erin Gallagher: They’re targeting the medical facilities such as public and private hospitals and field hospitals, and we’ve even seen vaccination clinics, children’s clinics and eye clinics. The facilities are being targeted by aerial bombs – cluster and barrel bombs, along with shells – and then some [on-foot] storming and arson.

That’s what’s happening in all the populated areas, from Aleppo to Homs, Hama, Damascus, Idlib, Latakia and Deir Ezzor. There’s only two places in the country where we don’t have any reports of attacks – Hassakeh and Sueda. So it’s been all over the country, and 90 percent of it has been committed by the Syrian government. Only 10 attacks we’ve heard of have been made by opposition groups, carried out by either the Islamic State of Iraq and the Levant, Jabhat al-Nusra or the Free Syrian Army.

Medical personnel themselves are also being attacked and targeted, through arrests, imprisonment, torture and executions. They are also being shelled while they’re working in hospitals, or trying to get patients out of an area. All of our figures show that the government is the party committing these crimes.

Syria Deeply: What types of violations are included on the map?

Gallagher: We know there are more attacks on medical facilities than what we’ve shown on our map. We’re only showing the ones that violate international humanitarian law. We’re just showing attacks that have occurred on functioning hospitals: when they’ve become militarized and are no longer used as hospitals, we don’t count them. These are purely the illegal, unlawful attacks.

Most of them appear to be targeted, so either the government has used weapons that can hit a target, like missiles and shells, or even a bomb dropped low enough by a helicopter. They’ve hit hospitals multiple times – we have several hospitals that were hit four times – and that can’t be by accident. We have hospitals located in fairly remote areas with nothing else nearby, so there can be no explanation for targeting something else and accidentally hitting the hospital instead.

Syria Deeply: Are the attacks equally spread between rural and urban areas?

Gallagher: The other portion of hospitals hit are those in densely populated civilian areas, and there are no precautions made to distinguish the hospitals from anything else around them, to protect the civilians in surrounding buildings – just reckless attacks.

Syria Deeply: How do you verify the information?

Gallagher: We’ve tried to use multiple independent sources – usually it’s three, or it could be one or two very credible detailed sources. Our numbers are conservative, we think it’s just a start. We had to stop collecting info at the end of March so that we could start working with the data we had, but we have already have heard of 20 attacks in April alone. So this has really become the norm in Syria, to attack the facilities.

We just heard today of two doctors that were killed, and we know that there’s been 49 medical personnel killed so far in 2014. Half of these were killed while working in facilities, and others via torture.

Syria Deeply: Have certain areas taken the brunt?

Gallagher: Rif Damascus has been hit very hard, and Aleppo and Homs as well. It’s a combination of these areas being both crowded, and opposition strongholds. Of the doctors who are left, many have fled and gone to practice in another area of the country, and then that area gets attacked, so they continue to move.

My guess is that the ones who are still working inside are there for the duration. I think their biggest day-to-day struggle is trying to perform the actual medical work. They don’t always have the equipment they need, whether that’s anesthesia or antibiotics. They have to perform medical work that’s often outside their expertise. On top of it, they’re worried about bombings, so they set up field hospitals in basements – not ideal conditions. So they’re working under very difficult circumstances in besieged areas, and they have to worry about their families and being able to make a living. And about being able to survive themselves.